Power transmission



Feb. 2, 1943. R RTL 2,310,124

POWER TRANSMISSION Filed July 24, 1940 2 Sheets-Sheet 2 Fla?) RAPID ADVANCE 4 INVENTOR ROBERT A. SHARTLE BY z 5 ATTORNEY Patented Feb. 2, 1943 POWER TRANSMISSION Robert A. Shartle, Rockford, m., assiinor to Vickers Incorporated, Detroit, Mich, a corporation of Michigan Application July 24, 1&0, Serial No. 347,253

5 (Balms. (C1. -136) with the work together with hydraulic control 'of a rotary drive for the tool. In a tapping machine it is desirable to permit the tapping tool to determine its own speed of advance by the pitch of the thread which it is cutting. Thus, the tool can act as the feeding means for determining the longitudinal advance of the tool carrying slide during the working stroke. It is necessary, however, that the tool slide be retracted to bring the tool out of the work a sufficient distance to permit removal of the work and replacing the new work piece in position. This necessitates additional power-operated means for reciprocating the slide in addition to the tapping tool itself. Automatically controlled tapping machines, wherein the tool is advanced rapidly to the work and then permitted to determine the rate of speed of the tool carriage during the working stroke, have been heretofore constructed but have embodied considerable complex mechanism, particularly where hydraulically operated.

It is an object of the present invention to provide an improved hydraulic .driving and controlling system for a tapping machine wherein the cycle of tool movement is controlled automatically by relatively simple control mechanism.

A further object is to provide an improved hydraulic circuit for actuating a plurality of motors under the conjoint control of a plurality of valves;

Further objects and advantages of ,the present invention will be "apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the present invention is clearly shown.

In the drawings:

Figure 1 is a diagrammatic view of a power transmission system embodying a preferred form of the present invention.

Figures 2 through '7 are schematic views of the circuit showing the parts in difierent positions at various stages in the cycle of operation.

Referring now to Figure 1 there is illustrated a vertically reciprocating slide l8 mounted in suitable ways on a machine frame, not shown, and carrying a rotatable tool spindle [2. The latter has a tapping tool I4 carried by the end thereof. The spindle I 2 is provided with the usual splines l6 whereby the spindle may be rotated through the gearing l8. The latter may be driven by an electric motor 20 which drives a clutch 22 from which the drive is carried through gearing l8 by means of customary electro-reverse gearing indicated at 24.

The slide I0 is adapted to be operated by a piston 26 having a rod 28 secured to the slide Ill. The piston and rod reciprocate in a cylinder 30 which, due to the rod projecting from the lower end thereof, is of the differential area type. The slide l0 may carry an upwardly extending arm 32 on which are positioned various cams 34, 36 and 38 adjustably mounted thereon for a purpose later to be described.

The clutch 22 may be operated by means of a hydraulic cylinder-and-piston motor 4|! while the reverse gearing 24 may be operated by a cylinder-and-piston motor 42. The three hydraulic motors described may be supplied with fluid from a fixed displacement pump 44 driven by a suitable prime mover such as an electric motor 46. The suction side of pump 44 withdraws oil from a tank 41 through a suction conduit 48. The delivery side of the pump is connected by means of a delivery conduit 50 to the customary relief valve 52 and then by a conduit 54 to the pressure port of a four-way valve 56. The latter may be of any suitable solenoid-operated, springcentered, open-center type as is well known in the art.

The tank ports of valve 56 are connected to tank by a conduit 58. The righthand cylinder port connects by a conduit 60 with the upper end of cylinder 48. Branch conduits 62 and 64 provide connections between conduit 68 and the lower end of cylinder 30 and the pressure port of a three-way valve 66. The latter is of the solenoid-operated, spring-offset type. The lefthand cylinder port of valve 56 connects by aconduit 68 with the lower end of cylinder 40. The cylinder port of valve 66 connects by a conduit 18 with the upper or large end of cylinder 88, the tank ports of valve 66 being connected to tank by a conduit 12.

Incorporated in conduit 68 is a pressure-responsive sequence valve 14 which, when the pres sure in conduit 68 rises to a predetermined value, opens communication between conduit 68 and a conduit 16. The latter leads to the presports connect to opposite ends of motor 42 byconduits 92 and 94.

For the purpose of controlling the solenoids 99, 99, 99 and 92 which operate the valves 99, 99, and 19, respectively, a control circuit is provided as follows: From one side of a suitable source of electric current supply designated as L a normally-open, two circuit, momentary-contact switch 94 is adapted to establish connections to two conductors 99 and 98. The conductor 99 extends to a single-pole, double-throw switch 99 adapted to be tripped by the cam 99 when the slide I9 reaches a point where the tool I4 is about to engage the work. The switch 99 may be of the snap-acting type although for simplicity of illustration it is not thus shown. In the position illustrated, the switch 99 establishes contact between conductor 99 and a conductor I99 extending to the solenoid 99, and to the other side of the power supply designated L Parallel with the switch 94 there is provided a normally-closed limit switch I92 which is held open by the cam 99 when the slide is in the position illustrated on the drawing. The switch I92, when closed, completes a circuit from line L to conductor 99 which effectively shunts the upper circuit of switch 94.

The conductor '98 extends to the operating coil of a holding relay I 94, the holding circuit I99 of which is normally closed through 8. normally-closed manual switch I99 and a-normallyclosed limit switch II9, the latter being opened by the cam 94 when the slide I9 reaches a position where the work is completed. The relay I94, when energized, is adapted to close a circuit extending from line. L by a conductor 2 to the solenoids 99 and 92. The switch 99, when shifted, is adapted to establish a circuit extending from conductor 99 through a conductor II4 to the solenoid 99.

In operation, with the parts in the position shown in Figures 1 and 2, the device is in its at-rest position, the full delivery of pump 44 passing through conduits 59 and 54, through the valve 99 to the tank port, and through conduit 99 to the tank 41. The pump is thus effectively bypassed, and no fluid is delivered to any of the hydraulic motors.

When it is desired to start a cycle of operation consisting of a rapid advance movement, inward and outward feeding movement,'and rapid return, the manual switch 94 may be closed to condition the circuit for the How conditions illustrated in Figure 3. This energizes solenoid 99 throughconductors 99 and I99 thereby shifting the spool of valve 59 to the left and admitting pressure oil from conduit 54 to conduit 99 where it flows to the upper end of cylinder 49 and to the small end of cylinder 99. The closingof switch 94 also establishes the initiating circuit 99 for relay I94 which accordingly becomes energized and establishes its own holding circuit I99 as well as energizing solenoids 99 and 92 through conductor H2.

The spools of valves 99 and 19 are accordingly shifted to the right, the former establishing connection between conduits 94 and I9 to thereby admit pressure 011 to the large end of cylinder 99. With the same pressure applied to both ends of this cylinder, the slide I9 is accordingly advanced rapidly, the oil discharged from the small end being returned through conduits 92,

99 and 94 through the conduit III to the large end. Thus the slide I9 is advanced downwardly at a speed determined by the eflective area of the rod 29 with respect to the delivery capacity of pump 44. Motor 49 is held with its piston in the downward position in which clutch 22 is disengaged so that there is no rotary motion of the tool I4. Shifting of valve 19 establishes a connection from conduit 19 to conduit 94 which connection is ineflective, however, because there is no pressure in conduit 99 to open valve I4. As the slide I9 advances downwardly, the tool is brought into engagement with the work at which point the cam 99 trips the switch 99 to deenergize solenoid 99 and to energize solenoid 99 through conductor 4. It will be noted that conductor 99 still remains connected to line L after switch 94 has been released because the cam 99 slides oil the limit switch I92 during the flrst movement of the slide I9 downwardly.

Energization of the solenoid 99 shifts the spool of valve 99 to the right connecting conduit 99 to tank and admitting pressure fluid from conduit 54 to conduit 99. This pressure fluid flrst flows through conduit 99 to the lower end of motor 49 thus shifting the piston thereof upwardly to engage the clutch 22 as shown in Figure 4. As soon as this movement is completed,

the pressure in conduit 98 builds up to'open valve 14 thereby admitting pressure oil to conduits 19 and 94 as shown in Figure 5. The piston of motor 42 is accordingly projected upwardly to shift the reversing mechanism 24 to the position of forward rotation of the tool I4. The latter accordingly begins its cutting work and forms the sole driving means for advancing the slide I9 further downwardly.

It will be noted that, in this position of the parts, the two ends of cylinder 99 are connected together through conduits 92, 99, 94, valve 99 and conduit 19. Thus, oil is free to pass from one end of the cylinder to the other without imposing any significant drag on the downward movement of slide I9. As the slide I9 reaches a point where the work is completed, cam 94 contacts limit switch II9 opening the latter to deenergize the holding relay I94. The latter accordingly deenergizes solenoids 99 and 92 permitting the spools of valves 99 and 19 to return to their lefthand position. This is shown in Figure 6.

Shifting of valve 99 closes the direct connection between conduits 94 and 19, but the two ends of cylinder 99 remain connected together through valves 99 and 99 and the tank. Thus the large end of cylinder 99 is now connected to tank through conduit I9 and the tank conduit I2. Likewise, the small end of cylinder 99 is connected to tank through conduits 92, 99, valve 59 and conduit 99.

The shifting of valve 19 reverses the fluid connection to motor 42 thereby admitting pressure.

oil from conduit 19 to conduit 92, returning the piston 42 downwardly and shifting the reversing mechanism 24 for reverse rotation of tool I4. It will be noted that the cylinder 49 remains connected as before since its direction of movement is controlled by the valve 99. Accordingly, the tool I4 is driven reversely to gradually feed the same out of the work and to feed the slide II upwardly at the same time.

As the tool leaves the work, th cam 99 shifts switch 99 to again deenergize solenoid 99 and energize solenoid 99. As shown in Figure 7, pressure oil is again directed from conduit 94 to conduit GI where it shifts the piston 01' motor 40 downwardly to disengage clutch 22. When this is done, the pressure is transmitted through branch 62 to the lower end of cylinder 30 to raise the piston 26. Since valve 68 is in its lefthand position, the large end of cylinder 30 remains connected to tank through conduits Ill and 12. Thus the slide I is rapidly returned until a point is reached where cam 38 opens limit switch I02 to deenergize solenoid 88. The parts are thus restored to their original position, and another cycle may be repeated by again closing the switch 9|. p

It will be seen that, by the use of a difierential-area motor at the cylinder 30 and by the particular arrangement of valves 58 and 66, .a circuit has been provided wherein the valve 58 not only controls the direction of movement of motor Ill but also controls the action of difl'erential motor 30. Thus when the valve 56 is shifted to the position for diseng gin the clutch, it also supplies pressure fluid for operating the differential motor ill. When the valve 56 is shifted reversely to engage clutch 22, it permits the motor 3! to float on the line, that is, it is bypassed. Likewise, the valve 68 controls the direction of operation of motor 30 during those parts ot the cycle when valve 58 directs fluid for operation of motor 30. During the other parts of the cycle, valve i6 is ineffective to prevent bypassing of cylinder 30. It will be seen that cylinder 30 is thus under the conjoint control of valves 56 and I.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understoodthat other'forms the scope forwardly to a predetermined position, means.

controlled thereby for bypassing fluid around the spindle translating means, and means also controlled by said element for initiating forward rotation of the tool.

2. Ina tapp machine having a rotatable means for controlling the direction of rotation of the spindle, a valve connected to control the supply of fluid both to the actuating means and the rotation controlling means, a second valve in series between the first valve and one of said actuating means, and connections providing for both forward and reverse motion of one actuating means while the other actuating means is movhig in a single direction.

3. In a. tapping machine having a rotatable and translatable tool carrying spindle the combination of hydraulically actuated means for translating the spindle to bring the tool into and out of engagement with the work, andmeans respon-' nect said end either-to the small end or to the low pressure side of the sourceindependently of the small end, a four-way reverse valve connected between opposite sides of the source and opposite sides of the other motor, and-a conduit connecting the small end of the differential motor to one side of the other motor whereby the diii'erential motor may be operated forward or reversely while the other motor is operated in one direction and the differential motor is bypassed while the other motor is operated in the opposite direction.

' 5. A hydraulic power transmission system comprising a pair of reversible fluid motors, one of which is of the diflerential-area cylinder-andpiston type, means forming a unitary source of pressure fluid for operating said motors, a fourway vvalve connected between opposite sides of the source and opposite sides of the other motor, conduits connecting both ends of the diflerential motor to one side of the other motor, and means in one of said conduits for selectively cutting off communication with the other motor and conand translatable tool carrying spindle the combination of hydraulically actuated means for translating the spindle, hydraulically actuated necting one end of the difl'erential motor to one side of the source whereby the differential motor may be controlled both by the four-way valve and by said means.

- ROBERT A. SHARTLE. 

